The present invention relates to an image forming apparatus for reading image information of a document and, more particularly, to an image forming apparatus capable of forming on a copying paper sheet a visible image corresponding to the image of the document.
In a conventional image forming apparatus such as an electronic copying apparatus, a document table is fixed on a housing. A document is placed face down on the document table such that a surface to be copied is in contact with the upper surface of the document table. In addition, the document is generally covered with a document cover. Therefore, the operator does not know how the image of the document is copied on the copying sheet until the copied sheet is discharged.
The copying operation is properly performed when the image on the document is concentrated at a central portion. However, when an image extends throughout a possible copying area of the document table and the document is slightly misaligned with respect to a reference position, part of the image copied from the document is lost. In addition to this disadvantage, the operator cannot accurately know which part of the document is enlarged in an enlargement mode. Therefore, this type of copying operation depends on guesswork. In other words, the operator places the document on the document table in roughly the right place. When the image on the copied sheet is faulty or when the document is not completely copied, the operator slightly moves the document with respect to the reference position so as to eliminate the fault or missing portion.
In this manner, when the operator performs a copying operation using the conventional electronic copying apparatus, operational mistakes frequently occur.